DYNAMIC SPECTRA OF PULSAR SCINTILLATIONS AT FREQUENCIES NEAR 0.34,0.41,0.63,1.4,1.7,3.2 AND 5.0 GHZ

We give examples of the dynamic spectra of the interstellar scintillations of radiation received from the pulsars PSR0628—28, 0833-45, 0834+06, 0950 + 08, 1451-68, 1642-03, 1749-28, 1919 +21 and 1929 + 10. The auto-covariance of the intensity is calculated as a function of separation in time and frequency to yield scattering parameters for eight of these pulsars and for PSR 1933 + 16. For PSR 0833 - 4 5 the details of the shapes of the auto-covariance functions, and the scaling with frequency, are compared with theory. It appears that further development of the theory is needed before comparisons of this form can give information on the distribution of the scale sizes of the irregularities in the interstellar ionized gas. For two pulsars, PSR 0628-28 and PSR 0834 + 06, systematic patterns of drifting bands were found in the dynamic spectra. The occurrence of such spectra implies that on these occasions the radiation reached the Earth predominantly from a few directions only. We discuss the implications of this result for the distribution of irregularity scales in the interstellar medium. © Royal Astronomical Society.